PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

Modern soybean cultivars should have good agronomic performance in addition to high bioactive properties. This study evaluated anthocyanin content, isoflavone composition, antioxidant activity, and agronomic traits of sixteen black soybean genotypes grown in Mojokerto, East Java, Indonesia. Seed samples were analysed for total anthocyanin content (TAC), antioxidant activity, and isoflavone composition, including daidzein, glycitein, and genistein, in both the seed coat and the cotyledon. Significant variation was observed among genotypes for all biochemical and agronomic traits. TAC was higher in the seed coat than in the seed cotyledon. Genotypes with black seed coats exhibited high TAC in the seed coat, whereas green cotyledon genotypes showed higher TAC in the cotyledon. Isoflavone concentrations ranged from 9.42–27.94 mg/kg for daidzein, 25.18–67.14 mg/kg for glycitein, and 12.93–34.52 mg/kg for genistein. Antioxidant activity in the cotyledon was generally low, while the seed coat exhibited antioxidant activity ranging from low to strong, with three genotypes classified as having strong antioxidant potential. The number of nodes was identified as a useful selection criterion for high-yielding genotypes. The Genotype-by-Trait (GT) biplot showed that the genotype G2 (JPG 15/Anj-884) had the highest values for all isoflavone compositions. Genotypes G6 (Khl/Anj-890), G7 (Khl/Anj-891), and G8 (Khl/Anj-893) performed best in terms of seed yield and antioxidant activity. Genotypes G9 (Khl/Anj-894), G11 (Khl/Anj-896), and G15 (Mallika) had large seed size and high TAC in both seed and cotyledon. These genotypes have potential for further improvement, either as promising lines or parental lines in developing new black soybean cultivars.